1. Field of the Invention
The present invention relates to a flow control valve and flow control valve apparatus, and more particularly, to a miniaturized flow-control valve to precisely control a flow rate and a flow control valve apparatus utilizing such a flow control valve.
2. Description of the Related Art
Flow control valves and apparatuses using flow control valves for controlling fluid flowing through a flow channel have been applied to many industrial fields including the manufacture of household appliances.
In general, a conventional flow control valve apparatus controls flow by moving a pin shaped valve rod from an orifice a predetermined distance to linearly control the opened area of the orifice. Typically, a valve rod is connected to a gear, which is connected to a rotor shaft of a stepping motor. The displacement of the valve rod can be varied in proportion to the number of pulses of the driving power. However, such a flow control valve apparatus has a high production cost due to the relatively high price of a stepping motor as well as the difficulty in hermetically sealing the rotor shaft of the stepping motor and the flow channel where the valve rod is positioned.
Another type of flow control valve apparatus has a diaphragm or a membrane installed in a part of the valve rod, wherein a compressive space is provided on a rear surface of the diaphragm or the membrane. The diaphragm deforms because of an expansion pressure, which is due to the heating of a fluid filled in the compressive space. This deformation resultingly controls the displacement of the valve rod. However, this flow control valve apparatus is difficult to miniaturize due to the addition of the separate compressive space. Furthermore, a valve response speed for a linear operation is lowered by using an expansion pressure caused by the heating of the compressive space. Accordingly, power consumption is increased due to the heat radiation necessary to maintain the valve's response speed.
Another type of flow control valve uses a solenoid coil. However, this type has difficulty in the linear control of the fluid due to an instable valve rod, and has problems of complicated parts and serious noise occurrence during the opening and closing operation thereof.
There is another type of conventional art flow control valve, which is manufactured by a micro-machining technology and which controls the flow rate by driving a diaphragm or flap formed on a location spaced away from an opening of the valve. That is, the opening of the valve is controlled by driving the flap or diaphragm. In order to drive the flap or diaphragm, a variety of driving methods such as an electrostatic driving method, a heat driving method, a piezoelectric driving method, and the like have been used.
In this type of flow control valve, input and output flow channels are not arranged in a straight line but in parallel in a direction where the fluid is inputted or outputted. Accordingly, there is a limitation in controlling the flow rate even when the flow rate is controlled by the diaphragm or flap. Furthermore, an analog method is proper for driving the diaphragm or flap rather than a digital method.